Supporting system for a floating unit in shallow or very shallow water

ABSTRACT

A supporting system for a floating unit in shallow water exerts controlled stresses on the floating unit hull and includes supporting structure for the hull. An extendable supporting device operatively connects to the supporting structure and is suitable to support a predetermined weight of the floating unit and load when entirely supported by the extendable supporting device and when the extendable supporting device rests on a bed of a water body. An actuator device connects to the supporting structure and operatively connects to the extendable supporting device for extension or contraction. A control device operatively connects to the actuator device to control the extraction or contraction movement of the extendable supporting device. The system includes at least one hull stress monitoring device operatively connected to the control device. A device to monitor the stress, or load, on the extendable supporting device operatively connects to the control device.

FIELD OF THE INVENTION

The present invention relates to a supporting system for floating units.

In particular, the present invention relates to a supporting system for a floating unit and to a floating unit suitable for shallow or very shallow water, e.g. water even only a few meters deep, typically strongly influenced by very high tide excursions.

Even more particularly, the present invention also relates to a method for supporting floating units on the bed of a water body, e.g. the sea bottom or the river bed, as well as a servicing method of a supporting system for floating units and also a method for reconfiguring floating units.

BACKGROUND ART

One of the most critical conditions for the dimensioning of a barge working in shallow water, where a high tide excursion is additionally possible, is dictated by the possibility that the barge may need to be in the condition of having to rest the hull on the sea bottom or the river bed.

In order to prevent damage to the hull, in addition to suitable designing of the hull itself, which is not always easy or even feasible in the case of existing floating units, it is important to prepare the sea bottom in advance, e.g. to remove roughness and guarantee suitable planarity, thus avoiding localized damage to the bottom of the hull or global deformations to the structure of the floating unit itself.

Very often, in order to avoid these undesired drawbacks, it is envisaged to rest the floating unit, e.g. a barge, exclusively on low bearing capacity bottoms so as to distribute the weight and the load of the barge uniformly on the bottom of the hull itself.

In all cases, if the barge rests with its hull on the bottom or bed, the hull must be locally strengthened by proceeding on a case-by-case basis according to the morphology and the properties of the terrain, e.g. according to planarity, yielding, presence of rocks and to guarantee a distribution of the useful or service load, hereinafter indicated as useful load, in uniform manner on the entire structure of the barge. It is thus apparent that designing a new hull or modifying an existing hull will vary from application to application, thus making the reuse of the application means on different bottoms unlikely.

Floating units of this type are known for example from document GB1199360.

These known solutions are very disadvantageous both for the time needed to prepare the bottom or bed and for the environmental impact on large areas of the sea bottom, as well as for the need to make robust hulls which are complex and costly to manage, maintain and govern. However, this remains the only solution possible today if existing floating units are used, in particular barges with large or very large longitudinal and transverse extension of the load deck.

In different situations, e.g. in the case of deep water, it is known to use units, specifically platforms, provided with legs moveable in height and capable of supporting the entire weight of the platform itself as a whole raising it from the surface of the water. In these known solutions, instead of resting the hull uniformly on the bottom, e.g. the sea bottom, the hull is rested on legs, thus following possible deviations of the planarity of the local yielding of bottom itself in this manner.

These known solutions are mainly used for offshore drilling (jack-up) and for the construction of jetties. In these cases, the unit is completely raised from the water to be independent from the weather and sea conditions and remain stable during all processing operations.

In order to avoid planarity problems of the hull load deck, the number of legs must be usually limited to three so to have substantially isostatic structures, capable of guaranteeing system stability during installation and during working operations.

These known legs are particularly invasive structures which greatly encumber the load deck, thus heavily influencing the useful load arrangement design and the working operations of the platform itself.

The legs are generally actuated by means of electric motors provided with pinion engaged in a rack integral with the legs of the means. Such a movement allows to control the movements and the planarity of the floating structure during the step of resting of the legs of the bottom. The bearing capacity of the means is mainly due to the driving of the legs into the terrain of the bottom itself, operating as true foundations poles with penetration of even several meters into the bottom.

A solution of this type is known from document U.S. Pat. No. 8,336,388 by National Oilwell Varco. This known solution suggests to control the actuation of a single leg so as to avoid problems of instability, such as peak loads of the structure of the leg itself, which is naturally long to be able to work in deep waters (even tens of meters deep).

Similar solutions are known from US 2006/0062637 by OFFSHORE TECHNOLOGY DEV. PTE LT, which again relates to controlled movement solutions to avoid instability of the single leg, and from KR101270905B1.

In all cases, these known solutions do not guarantee that the stresses in the hull, by overcoming the resistance limits thereof, above all in cases in which the required load deck surface is particularly broad, do not cause a localized permanent formation or a twisting of the entire structure, in particular if applied to barges of considerable longitudinal and transverse dimensions, e.g. of length in the order of about one hundred meters and width of tens of meters.

Thus, the need is strongly felt for a supporting system for a floating unit in shallow or very shallow water which allows to avoid the preparation of the bed or bottom of the water body and which at the same time avoids the need to re-engineer the structure of the hull to limit its deformation in case of localized supports which are borrowed from offshore perforation platform solutions.

Equally, it is strongly felt the need to make a solution which allows to rest a barge on a bottom or bed of a water body generally a few meters deep, in stable manner also in case of resting on non-uniform terrain, avoiding the need to excessively strengthen the floating unit and thus make it heavier.

Indeed, both the solution of resting the entire hull of the barge on the bottom or bed of the water body and the solution of resting the hull of the floating unit on legs so as to make it come out of the water as a traditional jack-up is today unsuitable to limit the deformation of the structure of the hull itself.

Solution

It is the object of the present invention to devise and make available a system and a method which allow to solve the drawbacks described above.

Such an object is achieved by a system according to claim 1, a floating unit according to claim 7, a supporting method according to claim 9, a servicing method according to claim 11, and a method for reconfiguring a floating unit according to claim 13.

In addition to the other advantages which will be described in greater detail below, the suggested solutions allow to obtain a supporting system on the bottom or bed provided, among other advantages, with a control of the force which establishes the load to be applied to each extendable supporting device as a function of the limit stress which can be applied to the hull structure, thus allowing to obtain light hull structures and which can be easily suitable to different types of bottom having non-uniform local supporting features.

The suggested solution is particularly suitable for hulls of large transverse and longitudinal breadth, such as barges which require a high number of supporting legs making the supported structure isostatic.

Furthermore, the suggested solution allows to redistribute the weight of the barge on several supporting points, configured as surface foundation, thus distancing the bottom of the barge from the bed of the water body. By virtue of the suggested solution it is not necessary for the barge to come out of the water, possibly also relying on the residual thrust on the immersed part to reduce the load and the stresses on the structure of the vessel itself.

Some advantageous embodiments are the object of the dependent claims.

FIGURES

Further features and advantages of the system and method according to the invention will be apparent from the description provided below of preferred embodiments thereof, given by way of non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 shows a perspective view of a lay barge floating on a water body;

FIG. 2 shows a partial section view of the barge in FIG. 1, in which the sections show some parts of the supporting system partially extended and resting on the sea bottom;

FIG. 3 shows a perspective view from the bottom of the barge in FIG. 2 having the supporting system partially extended;

FIG. 4 shows an axonometric, partial section view of an extendable supporting device in partially extended position;

FIG. 5 shows three different steps of servicing of an extendable supporting device, the first in retracted position, the second supported by a suspension cable and free from the supporting bracket during the step of releasing the leg foot and finally during the lifting of the leg body through the deck of the floating unit, together with the extraction of the leg foot;

FIG. 6 shows a perspective view of a floating unit with a dashed line in which the supporting system is highlighted with the control circuit, actuation and control diagrammatically shown;

FIG. 7 shows a flow chart of the main steps of management and control of the supporting system;

FIG. 8 shows a partial section side view of a floating unit provided with a supporting device according to a further embodiment and a first step in which the unit is floating on the surface of the water body;

FIG. 9 shows a side view of the unit in FIG. 8 in a second position in which the water body has a shallower depth with respect to FIG. 8, and the unit rests on the bottom of the water body by means of extensible supporting devices.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS

With reference to figures and according to a general embodiment, a supporting system 1 for a floating unit 2, e.g. suitable for shallow or very shallow bottoms, comprises a least one portion of supporting structure 3 envisaged in its hull 4. Said system further comprises at least one extendable supporting device 5. Said at least one extendable supporting device 5 is operatively connected to said portion of supporting structures 3 so as to support part of the weight of the floating unit 2 and of the load 16 or useful load arranged on said hull when supported by said at least one extendable supporting device 5 and when said at least one extendable supporting device 5 rests on a bed 6 of a water body 7, e.g. a sea bottom.

Said system further comprises at least one actuator device 8 connected to said at least one portion of supporting structure 3 and is operatively connected to said at least one extendable supporting device 5 for the extension of the extendable supporting device 5 or its contraction or retraction.

Said assembly further comprises at least one control device 9 operatively connected to the actuator device 8 to control the extraction or retraction movement of said at least one extendable supporting device 5.

Advantageously, said system 1 further comprises at least one stress monitoring device present in the hull or hull stress monitoring device 10, operatively connected to said at least one control device 9.

As additional advantage, said system further comprises at least one device to monitor the stress, or load, on the at least one extendable supporting device, said stress monitoring device is indicated in the accompanying figures with reference numeral 11 and is operatively connected to said at least one control device 9.

According to an embodiment, said system comprises at least one device for monitoring the trim of the hull 12 suitable to monitor the trim of the floating unit 2. Said at least one device for monitoring the trim of the hull 12 is operatively connected to said at least one control device 9. For example, said at least one hull trim monitoring device 12 comprises at least one inclinometer 13 suitable to detect the pitching, rolling and yawing of said hull 4. According to an embodiment, said at least one hull trim monitoring device 12 comprises at least two inclinometers 13 suitable to detect at least the pitching or rolling of the hull 4. According to yet another embodiment, said at least one hull trim monitoring device 12 comprises at least one gyroscopic device 14 suitable to detect the pitching, rolling and yawing of said hull 4.

According to an embodiment, said portion of supporting structure 3 comprises more than three leg seats 15, e.g. adapted to be arranged in said hull 4 so as to distribute the weight of said hull 4 and the useful load 16 arranged on said hull, thus preventing any overstressing of each portion of structure of said hull 4. According to a further embodiment, said more than three leg seats 15 are suitable to be arranged in said hull 4 so as to distribute the weight of said hull 4 and the useful load 16 placed on said hull, thus preventing any overstressing of said portions of supporting structure 3. According to an embodiment, said more than three leg seats 15 are six leg seats 15, e.g. distributed uniformly in the hull of the floating unit. According to an embodiment, said more than three leg seats 15 are eight leg seats 15, e.g. distributed uniformly in the structure of the hull of the floating unit.

According to an embodiment, said more than three of more leg seats 15 are accommodated in said hull so as to remain in operating conditions either retracted or extended entirely under the load deck so as to prevent cluttering of the load surface deck. According to an embodiment, said more than three leg seats 15 emerge under the hull and, for example but not necessarily, said more than three leg seats 15 are closed on top on their end facing towards the load deck by a supporting bracket 24, e.g. removable.

According to an embodiment, said extendable supporting device 5 comprises more than three extendable legs 17, each accommodated in its leg seat 15. According to an embodiment, said more than three extendable legs 17 are six extendable legs 17 accommodated in respective leg seats 15. According to a further embodiment, said more than three extendable legs 17 are eight extendable legs 17 accommodated in their respective leg seats 15 and uniformly distributed in the hull of the floating unit.

According to an embodiment, each pair of leg seats 15 and respective extendable leg 17 form a supporting unit 18 suitable to be installed in hulls 4 of floating units 2, e.g. already built and operating, allowing to retrofit the system 1, according to any one of the embodiments described ,on existing floating units.

According to an embodiment, each pair of leg seats 15 and respective extendable leg 17 constitute a supporting unit 18 suitable to be installed in hulls 4 of floating units 2 so as to prevent cluttering of the deck 19 used for the load 16 of the floating unit 2 both with the extendable leg 17 in the fully retracted position of the extendable leg 17 and in the fully extended position.

According to an embodiment, each pair of leg seats 15 and respective extendable leg 17 form a supporting unit 18 suitable to be installed in hulls 4 of floating units 2 so as to be always under the load deck 19 intended for the useful load 16 of the floating unit 2 in all conditions of use.

According to an embodiment, each of said more than three supporting units 18 comprises seat walls 19 which delimit a well-shaped seat. Connected to said seat walls 19 are guiding elements 21 to guide a leg member 22. At least one actuator assembly, for example at least one cylinder-piston assembly 23, is arranged between at least one supporting bracket 24, detachably connected to said seat walls 19, and said leg member 22 to extend or retract said leg member to or from said seat 19. According to an embodiment, each of said more than three supporting units 18 further comprises a leg foot 25 detachably connected to said leg member 22 and suitable to rest on the bed 6 or bottom, of the water body 7 distributing the load exerted by said extendable leg 17 on a wide surface.

According to an embodiment, each of said more than three supporting units 18 further comprises an actuation sensor 26 for detecting the action exerted by the at least one actuator assembly. For example, a pressure sensor of the control medium of the cylinder-piston assembly 23 is arranged operatively connected to each supporting unit 18.

According to an embodiment, each of said more than three supporting units 18 further comprises an extension sensor 27 to detect the position or travel or extension of said extendable leg 17. According to an embodiment, said at least one portion of supporting system 3 and the corresponding extendable supporting device 5 can be positioned in the hull so as to be integrated in the structure of the hull itself remaining within the clearance of the hull itself and avoiding resistances to navigation of the floating unit 2 when the extendable supporting device 5 is in retracted position. For example, according to an embodiment, the extendable supporting device has a leg foot 25 which in retracted conditions is accommodated in a leg foot seat so that the bottom of said foot reconstructs the continuity of the outer surface of the hull 4.

According to a further embodiment, said at least one extendable supporting device 5 comprises at least one inflatable device, e.g. an air cushion or airbag, or a water cushion, indicated hereinafter by reference numeral 28, connected to said portion of resting structure 3. Said portion of supporting system 3 comprises an airbag seat or a cushion seat 29 suitable to accommodate said cushion 28 when it is inflated or retracted condition and to rest the hull on said cushion 28 when the cushion is in inflated or extended condition and resting on the bed 6 of said water body 7. According to a further embodiment, said actuator device 8 comprises at least one inflation device, e.g. a compressor, in case of air, or pump, in case of water, indicated in the figures with reference numeral 30, suitable to inflate said at least one cushion 28. According to an embodiment, said at least one device for monitoring the stress, or load, on the at least one extendable supporting device 11 comprises at least one pressure sensor 31 suitable to measure the pressure in said cushion 28.

According to an embodiment, said at least one control device 9 is provided with feedback from the hull stress monitoring device 10, e.g. to define the entity of the load applicable to the at least one extendable supporting device 5 which does not produce an undesired stress on the hull.

The expression “feedback from the device” means the feedback of the signal produced by the device and proportional to the quantity detected thereby.

According to an embodiment, said at least one control device 9 is provided with feedback from the stress or load monitoring device of the at least one extendable supporting device 11, so as, for example, to interrupt the control of the actuator when a predetermined stress or load value is reached.

According to an embodiment, said at least one control device 9 is provided with feedback from the hull trim monitoring device 12, so as to extend the extendable supporting device seeking the desired trim of the hull, e.g. so as to keep the load deck of the hull either horizontal or parallel to the theoretical free water surface, mediating the swell of the water body, or again to arrange the barge at a predetermined distance from the bed of the water body.

According to an embodiment, said at least one control device 9 is provided with feedback from a device for monitoring the extension of the extendable supporting device 27, so as for example to interrupt the extension control when a predetermined travel value is reached or, for example, to compare the extensions of different extendable supporting devices and limit the differences of travel between these devices.

According to an embodiment, said system 1 further comprises a sensor for measuring the water level in the water body, suitable to verify the floatability of the floating unit according to the draft of its hull. According to an embodiment, said at least one control device 9 is operatively connected to said sensor for measuring the water level, so as to extend the at least one extendable supporting device 5 if the water level falls below a minimum value that would cause the hull 4 of the floating unit 2 to touch the bottom or bed 6 of the water body 7.

According to an embodiment, said hull stress monitoring device 10 comprises a database 32 which correlates at least two of the following values:

a predefined stress on the hull 4 in predefined sections or points of said hull;

a predefined load value for each extendable supporting device 5;

a predefined extension or travel value for each extendable supporting device 5;

a predefined value for the angle of trim of the hull 4;

a predefined useful load value 16.

According to an embodiment, said hull stress monitoring device 10 comprises a database containing for each predefined stress on the hull 4 evaluated in predefined sections or points of the hull itself, at least one maximum load value for each extendable supporting device 5 and/or at least one extension limit value of each extendable supporting device 5; and/or at least one maximum value for the angle of trim of the hull; and/or at least one maximum value for the useful load 16.

According to an embodiment, said hull stress monitoring device 10 comprises a structural model of the hull 4 so that each predefined stress on the hull 4 evaluated at sections or points of said hull defines a predefined load value for each extendable supporting device 5; and/or a predefined value for the extension, or travel, of each extendable supporting device 5; and/or a predefined value for the angle of trim of the hull 4; and/or a predefined value for the useful load 16.

According to a further embodiment, said hull stress monitoring device 10 comprises a structural model of the hull 4 which for each predefined load value of each extendable supporting device 5 defines a predefined stress value of the hull 4, evaluated at sections or points of the hull itself; and/or a predefined value for the extension, or travel, of each extendable supporting device 5; and/or a predefined value for the angle of trim of the hull 4; and/or a predefined value for the useful load 16.

According to an embodiment, said hull stress monitoring device 10 comprises at least one stress sensor, for example a strain gage 33, arranged in the structure of the hull arranged in predefined sections or at predefined points of the hull 4, e.g. the theoretical points of maximum stress of the hull structure 4.

According to an embodiment, said device for monitoring stress, or load, on the at least one extendable supporting device 11 comprises a load cell 34 suitable to measure the load applied to each extendable supporting device 5. According to an embodiment, said device for monitoring stress, or load, on the at least one extendable supporting device 11 comprises a stress sensor, for example a leg stress gage 33 arranged in the structure of the extendable supporting device 5.

The present invention relates also to a floating unit 2 comprising at least one assembly 1 as defined in any one of the embodiments described above.

For example, the present invention relates to a floating unit 2, which comprises a barge for low or very low water, e.g. a barge of considerable longitudinal and transverse extension, e.g. a barge suitable to install cables or wires or to bury them.

A method for supporting a floating unit 2 on the bed 6 of a water body 7 will be described below.

Said method, according to a general embodiment, comprises the steps of:

providing a system 1 having at least one supporting structure 3, e.g. having more than three portions of supporting structure 3 and having at least one corresponding extendable supporting devices 5, e.g. having more than three corresponding extendable supporting devices 5;

defining a load to apply to each extendable supporting device 5 as a function of a predefined maximum stress on the hull calculated or predefined in a predefined section or point of the structure of the hull of the floating unit 2;

controlling the extension, or retraction, of said extendable supporting devices 5 so as to apply the defined load for each extendable supporting device 5;

measuring the load applied to each extendable supporting device 5;

checking that the load applied to each extendable supporting device 5 is less than a predefined maximum value.

Further embodiments of the supporting method will be described below.

For example, a further supporting method comprises the further steps of:

defining a load to be applied to each extendable supporting device 5 also considering the useful load 16.

According to a further embodiment of the method, the following steps are provided:

defining a load to be applied to each extendable supporting device 5 also taking into account the trim of the hull 4 of the floating unit 2.

According to a further embodiment of the method, the following steps are provided:

providing with feedback the extension control of said extendable supporting devices 5 based on the measurement of the load applied to each extendable supporting device 5.

According to a further embodiment of the method, the following steps are provided:

providing with feedback the extension control of said extendable supporting devices 5 based on the calculation of the trim of the hull 4.

According to a further embodiment of the method, the following steps are provided:

interrupting the extension of the extendable supporting devices 5 upon reaching the defined load and/or a predefined maximum load for each extendable supporting device 5.

According to a further embodiment of the method, the following steps are provided:

checking the load applied to each extendable supporting device 5 at any change in floating conditions, or absence of floating, of the floating unit 2 and if the value of the load applied to each extendable supporting device 5 exceeds a predefined maximum load value for each extendable supporting device 5, redefining a new load to be applied to said extendable supporting device 5 and controlling the extension, or retraction, of said extendable supporting device 5 so as to apply the newly defined load to each extendable supporting device 5.

According to a further embodiment of the method, the following steps are provided:

checking whether the level of the water body 7 is above the maximum limit extension which can be reached by said extendable supporting device 5 and retracting said extendable supporting device 5.

According to a further embodiment of the method, the following steps are provided:

checking whether the level of the water body 7 is below a predefined maximum limit for the correct floating of the floating unit and extending said extendable supporting device 5.

Hereinafter, a method of servicing of a system 1 as defined in any one of the embodiments described above is described. Said method comprises the steps of:

raising at least one of said supporting units 18 and removing it from the respective leg seat 15 even with the floating unit 2 in use.

According to a further embodiment of the method, the following steps are comprised:

hooking a hoisting device 36 to the leg member 22;

disconnecting the cylinder-piston assembly 23 from the supporting bracket 24;

removing the supporting bracket 24 from the well-shaped seat 20;

disconnecting the leg foot 25 from the leg member 22;

removing the leg member 22 from the well-shaped seat 20 and lifting it onto the load deck 37.

A method for reconfiguring a floating unit 2 will be described below. Said method comprises the steps of:

providing at least one supporting structure 3 in the hull 4 of the floating unit 2;

connecting at least one system as described in any one of the claims described above to said supporting structure 3.

A person skilled in the art may make many changes, adaptations and replacements to the embodiments described above or can replace elements with others which are functionally equivalent in order to satisfy contingent needs without however departing from the scope of protection of the appended claims.

By virtue of the solutions described above, the extendable supporting device 5 will be driven limitedly inside the bed of the water body, e.g. by a few meters and consequently the necessary further excursion length of each extendable supporting device 5 will be advantageously comparable, thus also by a few meters.

REFERENCES

-   1 system -   2 floating unit -   3 portion of supporting structure -   4 hull -   5 extendable supporting device -   6 bed -   7 water body -   8 actuator device -   9 control device -   10 hull stress monitoring device -   11 device to monitor the stress, or load, on the at least one     extendable supporting device -   12 hull trim monitoring device -   13 inclinometer -   14 gyroscopic device -   15 leg seats -   16 load or useful load or service load -   17 extendable leg -   18 supporting units -   19 seat walls -   20 well-shaped seat -   21 guiding elements -   22 leg member -   23 cylinder-piston assembly -   24 supporting bracket -   25 leg foot -   26 actuation sensor -   27 extension sensor -   28 airbag or cushion -   29 cushion seat -   30 compressor -   31 pressure sensor -   32 database -   33 strain gage -   34 load cell -   35 leg stress gage -   36 hoisting device -   37 deck of the hull 

1. Supporting system for a floating unit in shallow water, comprising: at least one portion of supporting structure for a hull of said floating unit; at least one extendable supporting device operatively connected to said portion of supporting structure and suitable to support part of weight of the floating unit and of a load arranged on said hull when supported by said at least one extendable supporting device and when said at least one extendable supporting device rests on a bed of a water body; at least one actuator device connected to said at least one portion of supporting structure and operatively connected to said at least one extendable supporting device for extension or retraction of said at least one extendable supporting device; at least one control device operatively connected to said actuator device to control the extraction or retraction movement of said at least one extendable supporting device; at least one hull stress monitoring device operatively connected to said at least one control device; and at least one device to monitor the stress, or load, on the at least one extendable supporting device operatively connected to said at least one control device.
 2. System as claimed in claim 1, further comprising: at least one device for monitoring trim of the hull of said floating unit operatively connected to said at least one control device; and/or wherein said at least one hull trim monitoring device comprises at least one gyroscopic device suitable to detect pitching, rolling and yawing of said hull.
 3. System as claimed in claim 1, wherein said portion of supporting structure comprises more than three leg seats; and/or wherein said more than three leg seats are suitable to be arranged in said hull so as to distribute the weight of said hull and the load arranged on said hull to prevent overstressing of each portion of structure of said hull; and/or wherein said more than three leg seats are six leg seats; and/or wherein said more than three leg seats are eight leg seats; and/or wherein said extendable supporting device comprises more than three extendable legs; and/or wherein said more than three extendable legs are six extendable legs; and/or wherein said more than three extendable legs are eight extendable legs; and/or wherein each pair of leg seats and respective extendable leg constitutes a supporting unit suitable to be installed in hulls of floating units already in use; and/or wherein each pair of leg seats and respective extendable leg constitutes a supporting unit suitable to be installed in hulls of floating units so as to prevent cluttering of the deck used for the load of the floating unit both with the extendable leg in the fully retracted position and in the fully extended position: and/or wherein each of said more than three supporting units comprises seat walls which delimit a well-shaped seat; guiding elements to guide a leg member; at least one actuator assembly comprising at least one cylinder-piston assembly, arranged between at least one supporting bracket, detachably connected to said seat walls, and said leg member to extend or retract said leg member; and/or wherein each of said more than three supporting units further comprises a leg foot detachably connected to said leg member and suitable to rest on the bed of the water body distributing the load applied by said extendable leg; and/or wherein each of said more than three supporting units further comprises an actuation sensor to detect action exerted by the at least one actuator assembly, the actuation sensor comprising a pressure sensor of a control medium of the cylinder-piston assembly; and/or wherein each of said more than three supporting units further comprises an extension sensor to detect position or travel or extension of said extendable leg; and/or wherein said at least one portion of supporting structure and the corresponding extendable supporting device are available in the hull so as to be incorporated in the structure of the hull and follow a profile of the hull without hindering the navigability of the floating unit.
 4. System as claimed in claim 1, wherein: said at least one extendable supporting device comprises at least one cushion connected to said portion of supporting structure comprising a cushion seat suitable to accommodate said cushion when in a deflated condition and to rest the hull upon said cushion when the cushion is in the inflated condition and resting on the bed of the water body; and/or wherein said actuator device comprises at least one compressor suitable to inflate said at least one cushion; and/or wherein said at least one device for monitoring the stress, or load, on the at least one extendable supporting device comprises at least one pressure sensor suitable to measure pressure in said cushion.
 5. System as claimed in claim 1, wherein: said at least one control device is provided with feedback from the hull stress monitoring device; and/or wherein said at least one control device is provided with feedback from the device for monitoring the stress, or load, on the at least one extendable supporting device; and/or wherein said at least one control device is provided with feedback from the hull trim monitoring device; and/or wherein said system further comprises a sensor for measuring water level in the water body, suitable to verify floatability of the floating unit according to draft of the floating unit; and/or wherein said at least one control device is operatively connected to said sensor for measuring the water level, so as to extend the at least one extendable supporting device if the water level falls to below a minimum value that would cause the hull of the floating unit to touch the bottom or bed of the water body.
 6. System as claimed in claim 1, wherein: said hull stress monitoring device comprises a database which correlates at least two of the following values: a predefined stress on the hull in predefined sections or points of said hull; a predefined load value for each extendable supporting device; a predefined extension or travel value for each extendable supporting device; a predefined value for the angle of trim of the hull; a predefined useful load value; and/or wherein said hull stress monitoring device comprises a database containing for each predefined stress on the hull in predefined sections or points of said hull, at least one maximum load value for each extendable supporting device; and/or at least one maximum value for the extension of each extendable supporting device; and/or at least one maximum value for the angle of trim of the hull; and/or at least one maximum value for the useful load; and/or wherein said hull stress monitoring device comprises a structural model of the hull which for each predefined stress on the hull at sections or points of said hull defines a predefined load value for each extendable supporting device; and/or a predefined value for the extension, or travel, of each extendable supporting device; and/or a predefined value for the angle of trim of the hull; and/or a predefined value for the useful load; and/or wherein said hull stress monitoring device comprises at least one stress sensor comprising a strain gage, arranged in the structure of the hull in predefined sections or at predefined points of the hull; and/or wherein said device for monitoring stress, or load, on the at least one extendable supporting device comprises a load cell suitable to measure the load applied to each extendable supporting device; and/or wherein said device for monitoring stress, or load, on the at least one extendable supporting device comprises a stress sensor comprising a leg stress gage arranged in the structure of the extendable supporting device.
 7. Floating unit comprising at least a system as described in claim
 1. 8. Floating unit as claimed in claim 7, comprising a barge for shallow or very shallow water.
 9. Method for supporting a floating unit on a bed of a water body, comprising: providing a system having more than three portions of supporting structure and more than three corresponding extendable supporting devices; defining a load to apply to each extendable supporting device as a function of a predefined maximum stress on a hull calculated or predefined in a predefined section or point of a structure of the hull of the floating unit; controlling extension, or retraction, of said extendable supporting devices so as to apply the defined load for each extendable supporting device; measuring the load applied to each extendable supporting device; checking that the load applied to each extendable supporting device is less than a predefined maximum value.
 10. Method as claimed in claim 9, further comprising: defining a load to be applied to each extendable supporting device taking into account trim of the hull of the floating unit; and/or further comprising: controlling the extension of said extendable supporting devices based on feedback on a measurement of the load applied to each extendable supporting device; and/or further comprising: controlling the extension of said extendable supporting devices based on feedback on a calculation of the trim of the hull; and/or further comprising: interrupting the extension of the extendable supporting devices upon reaching the defined load and/or a predefined maximum load for each extendable supporting device; and/or further comprising: checking the load applied to each extendable supporting device at any change in floating conditions, or absence of floating, of the floating unit; and if a value of the load applied to each extendable supporting device exceeds a predefined maximum load value for each extendable supporting device, redefining a new load to be applied to said extendable supporting device and controlling the extension, or retraction, of said extendable supporting device so as to apply the newly defined load to each extendable supporting device; and/or further comprising: checking that a level of the water body is below a predefined maximum limit for the correct floating of the floating unit and extending said extendable supporting device.
 11. Method of servicing a system as defined in claim 3, comprising: raising at least one of said supporting units and removing said at least one of said supporting units from the respective leg seat even with the floating unit in use.
 12. Method of servicing as claimed in claim 11, further comprising: hooking a hoisting device to the leg member; disconnecting the cylinder-piston assembly from the supporting bracket; removing the supporting bracket from the well-shaped seat; disconnecting the leg foot from the leg member; removing the leg member from the well-shaped seat and lifting the leg member onto the deck of the hull.
 13. Method for reconfiguring a floating unit comprising: providing at least one supporting structure in the hull of the floating unit; connecting at least one system as described in claim 1 to said supporting structure. 